Air flow into an engine may be controlled via a central or primary throttle that regulates air flow from an air filter of an air intake into an intake manifold and engine cylinders. The throttle may include an electric actuator, such as a motor, to regulate a position of a throttle plate of a butterfly valve. If a driver of the vehicle requests additional engine torque, the throttle opening amount may be increased. If the driver requests less engine torque, the throttle opening amount may be decreased. The throttle may include several sensors to verify that the throttle is performing as desired. If throttle operation is not as desired, it may be determined that the throttle is degraded. The throttle may be adjusted to a closed position where the throttle plate is positioned against a throttle stop when the throttle is determined to be degraded. A predetermined amount of air may pass through the throttle when the throttle is positioned against the stop. The predetermined amount of air allows the vehicle to travel at a very low speed so that the vehicle may be moved off the road it is traveling. Further, if desired, the vehicle may be driven a short distance to allow the driver to seek service for the vehicle. However, if the vehicle is being driven in a rural area, it may take a long period of time before the vehicle reaches an area where the vehicle can be serviced since the amount of engine torque available is low while the throttle plate is positioned against the stop.
The inventor herein has recognized the above-mentioned limitations and has developed an engine control method, comprising: opening a fuel vapor storage canister vent valve and closing a fuel tank vapor blocking valve via a controller in response to an indication of degradation of a throttle that regulates air flow from an engine air intake filter to cylinders of an engine.
By adjusting operating states of devices in a fuel vapor control system, it may be possible to provide the technical result of providing additional air flow to an engine during conditions where a throttle of the engine is degraded so that additional torque may be provided by the engine without having to operate the throttle. For example, the fuel tank vapor blocking valve may be closed and the fuel vapor storage canister vent valve may be opened to prevent fuel vapors from flowing to the engine while air flows to the engine via a passage leading from atmosphere through a fuel vapor storage canister and to the engine intake manifold. Thus, the possibility of over enriching engine cylinders may be mitigated while engine air flow may be increased so that the vehicle may reach a service facility in a timelier manner.
The present description may provide several advantages. In particular, the approach may provide improved vehicle drivability during conditions of throttle degradation. In addition, the approach may be provided with little expense since fuel vapor controls are common. Further, the approach provides for controlling fuel vapors while providing an alternative air flow path that is responsive to driver demands.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.